Resin sheet having controlled thermal conductivity distribution, and method for manufacturing the same

ABSTRACT

A resin sheet has a single composition, and changes in thermal conductivity according to an area. The resin sheet includes a region having a thermal conductivity that is greater than an average value of a thermal conductivity of an entirety of the resin sheet by 1 W/mK or more. A method for manufacturing a resin sheet includes: forming a resin composition into a molded body having a sheet shape, the resin composition containing a filler having magnetic anisotropy; performing magnetic field orientation on the filler by using a bulk superconductor magnet in one or a plurality of predetermined portions of the molded body; and forming a region having a thermal conductivity that is greater than an average value of a thermal conductivity of an entirety of the resin sheet by 1 W/mK or more, in the one or the plurality of predetermined portions.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2018-188049 filed in Japan on Oct. 3, 2018, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a resin sheet having a controlled thermal conductivity distribution, and a method for manufacturing the same.

BACKGROUND ART

In recent years, it has been requested that materials used in automobiles, airplanes, electronic components, and the like be improved in performance in various aspects. In particular, it has been requested year after year that the characteristics of a material used to radiate or insulate heat emitted from an electronic component, an apparatus, or the like be improved in performance. Above all, there is a need for a technique for controlling the thermal conductivity of a material at an advanced level, for example, in such a way that heat is radiated in a specified portion and heat is insulated in another specified portion.

An example of a method for controlling thermal conductivity is a method using a magnetic field (Patent Documents 1 to 3). The techniques of Patent Document 1 and Patent Document 2 disclose a method for forming a resin molded body in which an anisotropic filler has been oriented by using a superconducting coil magnet of 1.0 T. However, in these methods, fibers are uniformly oriented due to a uniform magnetic field of a superconducting coil, and an obtained sheet has a constant thermal conductivity. Therefore, it is difficult to control thermal conductivity at an advanced level. In addition, structurally, only a member that enters a bore of the superconducting coil magnet can be oriented. Patent Document 3 discloses a method for orienting ferromagnetic material-coated carbon fibers in a resin material. However, a filler fails to be sufficiently oriented without being coated with a ferromagnetic material, and a cost and the characteristics of a material are significantly restricted.

In addition, the use of a material that changes in thermal conductivity due to heat is also known (Patent Document 4). In this method, a change in thermal conductivity of a liquid crystal polymer due to heat is used. However, in this method, thermal conductivity fails to be significantly changed, and control fails to be performed according to an area.

Further, a method using the flow of resin is also known (Patent Document 5). This method is a method using a flow at the time of injection. In this method, fibers are oriented in accordance with a flow inside a mold at the time of injection molding. Therefore, it is difficult to completely control orientation in a specified shape. In addition, resin to be used is limited to resin having a high fluidity.

As described above, a technique is hardly known for controlling the thermal conductivity of a material to be used for a resin sheet according to a position, and there is a need to develop such a technique.

CITATION LIST

Patent Document 1: JP-A 2004-255600

Patent Document 2: JP-A 2006-335957

Patent Document 3: JP-A 2000-141505

Patent Document 4: JP-A 2016-56352

Patent Document 5: JP-A 2014-124785

SUMMARY OF THE INVENTION

The present invention has been made in view of the circumstances described above. It is an object of the present invention to provide a resin sheet in which thermal conductivity is controlled according to an area at an advance level, and a method for manufacturing the same.

The inventors have conducted intensive studies in order to achieve the object described above, and have discovered that a resin sheet that freely includes a portion having a high thermal conductivity in a thickness direction can be formed by locally performing magnetic field orientation on a resin composition having magnetic anisotropy, by using a bulk superconductor magnet. Thus, the inventors have completed the present invention.

Stated another way, the present invention provides a resin sheet and a method for manufacturing the same that are described below.

1. A resin sheet that has a single composition and that changes in thermal conductivity according to an area, wherein a region exists that has a thermal conductivity that is greater than an average value of a thermal conductivity of an entirety of the resin sheet by 1 W/mK or more. 2. The resin sheet described in the above 1, wherein a minimum unit area of the region having the thermal conductivity that is greater than the average value of the thermal conductivity of the entirety of the resin sheet by 1 W/mK or more is 0.2 cm² or more. 3. The resin sheet described in the above 1, wherein an area of the region having the thermal conductivity that is greater than the average value of the thermal conductivity of the entirety of the resin sheet by 1 W/mK or more is from 1 to 50% of an area of the entirety of the resin sheet. 4. The resin sheet described in the above 1, wherein the region having the thermal conductivity that is greater than the average value of the thermal conductivity of the entirety of the resin sheet by 1 W/mK or more includes a portion having a thermal conductivity of 5 W/mK or more. 5. The resin sheet described in the above 1, wherein a region having a thermal conductivity of 5 W/mK or more and a region having a thermal conductivity of 2 W/mK or more are included in both. 6. The resin sheet described in the above 1, wherein one or a plurality of regions exists that is spaced apart from an outer peripheral edge of the resin sheet, is surrounded by a closed loop, and has a thermal conductivity of 5 W/mK or more. 7. The resin sheet described in the above 6, wherein a minimum thermal conductivity of the one or the plurality of regions surrounded by the closed loop is different from a maximum thermal conductivity of a region outside the one or the plurality of regions by 3 W/mK or more. 8. A resin sheet that is obtained by cutting off the one or the plurality of regions having a thermal conductivity of 5 W/mK or more and being surrounded by the closed loop, described in the above 6 9. The resin sheet described in the above 1, wherein the resin sheet includes a cured product of a resin composition containing a filler having magnetic anisotropy. 10. The resin sheet described in the above 9, wherein the filler having the magnetic anisotropy has been oriented in a thickness direction of the resin sheet. 11. The resin sheet described in the above 9, wherein the filler having the magnetic anisotropy includes at least one filler selected from the group consisting of a carbon fiber, an alumina fiber, an aluminum nitride whisker, a metal nanowire, a carbon nanotube, a boron nitride nanotube, scaly boron nitride, plate-like aggregated boron nitride, scaly graphite, graphene, and plate-like alumina. 12. The resin sheet described in the above 1, wherein a resin component of the resin sheet includes a silicone resin or an epoxy resin. 13. The resin sheet described in the above 1, wherein a thickness of the resin sheet is 20 mm or less. 14. A method for manufacturing a resin sheet, the method including: forming a resin composition into a molded body having a sheet shape, the resin composition containing a filler having magnetic anisotropy; performing magnetic field orientation on the filler having the magnetic anisotropy by using a bulk superconductor magnet in one or a plurality of predetermined portions of the molded body; and forming a region having a thermal conductivity that is greater than an average value of a thermal conductivity of an entirety of the resin sheet by 1 W/mK or more, in the one or the plurality of predetermined portions. 15. The method for manufacturing a resin sheet described in the above 14, wherein the resin composition includes a liquid resin composition, the liquid resin composition is applied onto a film, the magnetic field orientation is performed on one or a plurality of predetermined portions of a body coated with the liquid resin composition, and the liquid resin composition is cured.

Advantageous Effects of the Invention

According to the present invention, a resin sheet that freely includes a portion having a high thermal conductivity in a thickness direction can be formed by using a magnetic field that is concentrated on a center of a bulk superconductor magnet. According to the present invention, a resin sheet can be provided that has a single composition and that changes in thermal conductivity according to an area. One feature of this resin sheet is that this resin sheet is not formed by joining resin sheets having thermal conductivities different from each other by using an adhesive or the like and this resin sheet has a single composition. As described above, according to the present invention, a resin sheet can be provided that freely includes a portion having a high thermal conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example for describing a method for measuring thermal conductivity, and a region below a dotted line (reference sign L) in this drawing indicates a resin sheet;

FIGS. 2A to 2C are conceptual diagrams illustrating an example of a region having a high thermal conductivity that is located inside an outer peripheral edge of a resin sheet and is surrounded by a closed loop, and FIGS. 2D to 2F are conceptual diagrams illustrating an example of a region having a high thermal conductivity that is surrounded in a state where a portion of the region crosses or overlaps the outer peripheral edge of the resin sheet;

FIG. 3 is a conceptual diagram illustrating a state of a magnetic flux density of a bulk superconductor magnet;

FIG. 4 is a side view of a resin molded body having a sheet shape;

FIG. 5 is a schematic side view illustrating an example of a manufacturing apparatus used in the present invention;

FIG. 6 is a schematic view illustrating a state in a case where magnetic field orientation is performed according to the present invention;

FIG. 7 is a conceptual diagram in a case where a magnetic field is applied to a resin molded body and a plurality of regions having a high thermal conductivity is generated on a sheet;

FIG. 8 illustrates a thermal conductivity distribution map in a thickness direction of a sheet in each position, the thermal conductivity distribution map being obtained in Example 1;

FIG. 9 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 2;

FIG. 10 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 3;

FIG. 11 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 4;

FIG. 12 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 5;

FIG. 13 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 6;

FIG. 14 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 7;

FIG. 15 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 8;

FIG. 16 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 9;

FIG. 17 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Example 10; and

FIG. 18 illustrates a thermal conductivity distribution map of a sheet in each position, the thermal conductivity distribution map being obtained in Comparative Example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described in more detail below.

A resin sheet according to the present invention is effectively used as a heat radiation sheet, and the resin sheet includes a region having a thermal conductivity that is higher than an average thermal conductivity of the entirety of the sheet by 1 W/mK or more. A variety of thermal conductivity characteristics can be imparted to the resin sheet according to the present invention in accordance with a situation of the use of a resin sheet including a region having a high thermal conductivity, as described above.

In the present invention, the thermal conductivity of a resin sheet refers to a thermal conductivity in a thickness direction of the resin sheet that has been measured according to the method described below.

Method for Measuring Thermal Conductivity

First, a resin sheet is sectioned into square regions having a fixed area, as illustrated in FIG. 1. Here, it is assumed that an end portion or a curve portion that fails to be sectioned to have a square shape is not a target to be measured. It is preferable that the area of a sectioned square be within a range of from 0.1 to 4 cm². From the viewpoint of easy measurement, it is preferable that the area be 1 cm².

A thermal conductivity in a thickness direction is measured for each of the square regions by using the laser flash method. The obtained value (W/mK) is rounded off to one decimal place.

A average value of the thermal conductivities of the respective regions that have been measured according to the method described above is a average thermal conductivity of the entirety of the sheet.

Here, to “include a region having a thermal conductivity that is greater than a average value of the entirety of the sheet by 1 W/mK or more” means that at least one of the sectioned square regions has a thermal conductivity that is higher than a “average thermal conductivity of the entirety of the sheet” by 1 W/mK or more.

It is preferable that the minimum unit area of the region having a thermal conductivity that is greater than the average value of the entirety of the sheet by 1 W/mK or more be 0.2 cm² or more. The minimum unit area according to the present invention means that the region described above is measured as a square region having an area of 0.2 cm² or more. In this case, it is more preferable that the minimum unit area be from 0.2 to 3 cm², and in particular, from 0.5 to 1 cm². Above all, from the viewpoint of heat radiation from only a specified portion, it is preferable that the area of a region having a thermal conductivity that is higher than the average thermal conductivity of the entirety of the sheet by 1 W/mK or more be from 1 to 50% of the area of the entirety of the sheet. It is more preferable that the area be from 5 to 45%. It is further more preferable that the area be from 15 to 40%. Further, it is preferable that the region having a thermal conductivity that is greater than the average value of the entirety of the sheet by 1 W/mK or more have a portion having a thermal conductivity of 5 W/mK or more. It is more preferable that the region have a portion having a thermal conductivity of 7 W/mK or more. It is further more preferable that the region have a portion having a thermal conductivity of 10 W/mK or more.

It is preferable that the resin sheet according to the present invention include one or a plurality of regions that is spaced apart from an outer peripheral edge of the resin sheet and is surrounded by a closed loop and that has a thermal conductivity of 5 W/mK or more. Specifically, when X is an arbitrary integer of 5 or more and one X is selected, it is preferable that the resin sheet include one or a plurality of regions that has a thermal conductivity of X W/mK or more with a closed loop as a boundary. In the present invention, “the resin sheet includes a region that has a thermal conductivity of X W/mK or more with a closed loop as a boundary” means that each of the square regions in which thermal conductivity has been measured has a thermal conductivity of X W/mK or more and that a boundary of continuous square regions that are adjacent to each other in vertical and lateral directions does not cross or overlap an outer periphery of the sheet so as to form a closed loop (FIGS. 2A to 2C). In this case, as illustrated in FIG. 2C, not all of the continuous square regions may have a thermal conductivity of X W/mK or more, and a region having a low thermal conductivity that is less than X W/mK may exist inside the continuous square regions (this is illustrated as if a hole were opened, in the conceptual diagram of FIG. 2C illustrating a resin sheet). Namely, this means that a region having a high thermal conductivity exists as a spot inside the sheet. On the other hand, FIGS. 2D to 2F illustrate examples of a region in which a portion having a high thermal conductivity crosses or overlaps the outer peripheral edge of the resin sheet.

In addition, from the viewpoint of further clarifying heat insulating property and heat radiating property, it is preferable that a minimum thermal conductivity inside the region with a closed loop as a boundary be different from a maximum thermal conductivity outside the region by 3 W/mK or more.

The region having a thermal conductivity of X W/mK or more described above may appropriately be cut out and used in accordance with a use situation. The thickness of the resin sheet is not particularly limited. However, from the viewpoint of thermal conduction, it is preferable that the thickness be not more than 20 mm, and it is more preferable that the thickness be not more than 5 mm. It is preferable that the thickness of the resin sheet be at least 0.05 mm, and particularly it is preferable that the thickness be at least 0.1 mm.

A resin composition used for the resin sheet according to the present invention may be selected from a thermosetting resin composition, a photocurable (UV-curable) resin composition, and an electron-beam curable resin composition. These resin compositions are solidified by being cured or being converted into a B-stage due to heating or the irradiation such as a UV laser, an electron-beam laser and the like.

The resin composition contains curable resin and a filler having magnetic anisotropy. The curable resin is not particularly limited. However, the illustrative examples of the curable resin include thermosetting silicone resin, thermosetting epoxy resin, UV-curable epoxy resin, UV-curable silicone resin, and electron-beam curable silicone resin. Of these resins, the use of the thermosetting silicone resin is preferable. In this case, as the curable resin, liquid resin may be used. The resin composition may be blended with a curing agent or an additive according to the type of curable resin. As characteristic properties of the curable resins after curing, any characteristic of a plastic state, a rubbery state, and a gel state may be adopted.

As the filler having magnetic anisotropy added to the resin composition, a filler is used that has crystal magnetic anisotropy and/or shape magnetic anisotropy and that is oriented in one direction by being applied with a magnetic field. Thermal conductivity can be controlled by controlling the orientation of the filler described above in one direction.

Illustrative Examples of a material having crystal magnetic anisotropy include a crystalline inorganic material and a crystalline organic material such as an organic single crystal. In addition, illustrative examples of the filler having shape magnetic anisotropy include: a fibrous substance such as a cellulose nanofiber, a carbon fiber, an alumina fiber, an aluminum nitride whisker, or a metal nanowire; a nanotube-based substance such as a carbon nanotube or a boron nitride nanotube; and a plate-like or columnar substance such as scaly boron nitride, plate-like aggregated boron nitride, scaly graphite, graphene, or plate-like alumina. It is preferable that the filler be a fibrous substance or a plate-like or columnar substance. From the viewpoint of thermal conductivity, it is particularly preferable that the filler be a carbon fiber.

Above all, it is preferable that a pitch-based carbon fiber be used that has a thermal conductivity of 500 W/mK or more in an axial direction. Also, the use of a carbon fiber having a length of 50 μm or more is preferable from the viewpoint of thermal conductivity.

The blending amount of the filler having magnetic anisotropy is preferably from 50 to 300 parts by weight, particularly from 75 to 200 parts by weight, per 100 parts by weight of the curable resin.

In order to, for example, improve the strength of a resin cured product, a filler without magnetic anisotropy, such as spherical silica, may be simultaneously used as the filler.

An example of a manufacturing method according to the present invention is described in detail below with reference to FIGS. 3 to 7.

Preferably, a resin sheet having thermal conductivities different from each other according to an area, as described above, is formed by partially performing magnetic field orientation on a filler having magnetic anisotropy inside the sheet, by using a bulk superconductor magnet.

The bulk superconductor magnet is used as magnetic poles by magnetizing a superconductor under a magnetic field of a superconducting coil or the like. Once magnetized, a magnet can be obtained that semipermanently has a high magnetic flux density in a cooled state. Examples of a magnetizing method include pulse magnetization and magnetization using a superconducting coil magnet. From the viewpoint of the magnitude of a captured magnetic flux density, it is preferable that magnetization be performed by using the superconducting coil magnet. It is preferable that a superconducting coil magnet used in magnetization have a magnetic flux density of 6 T or more. If the magnetic flux density is less than 6 T, a bulk superconductor magnet after magnetization may have an insufficient magnetic flux density.

As illustrated in FIG. 3, normally, the magnetic field of the bulk superconductor magnet is strong only in a center portion, and is perpendicular to a plane. Therefore, the bulk superconductor magnet is available in order to partially orient a target portion of the resin sheet and improve thermal conductivity.

A superconductor used for the bulk superconductor magnet is not particularly limited, but the use of a RE-Ba—Cu—O based superconductor (RE is at least one selected from Y, Sm, Nd, Yb, La, Gd, Eu, and Er), a MgB₂ based superconductor, a NbSn₃ based superconductor, an iron based superconductor, or the like are preferable. In view of a price, a simple manufacturing method, and a high magnetic flux density, the use of the RE-Ba—Cu—O based superconductor is more preferable.

The shape and size of the bulk superconductor magnet are not particularly limited, but, from the viewpoint of the strength of a magnetic field, the use of a disc-shaped bulk superconductor magnet having a diameter of 4 cm or more, particularly a diameter of from 5 to 12 cm is preferable.

First, as illustrated in FIG. 4, a sheet shaped resin molded body 3 made of the resin composition described above is prepared. It is also preferable that at least an upper face of the resin molded body 3 be covered with a cover material 2. In FIG. 4, upper and lower faces of the resin molded body 3 are covered with the cover materials 2 and 2. If the resin composition is exposed without being covered, since it is difficult to apply ultrasonic vibration, or the surface of resin is corrugated due to supersonic vibration with resulting in a non-uniform thickness, that is not preferable. The member selected from a resin film or a non-ferromagnetic metal plate is preferably used as the cover material. The illustrative examples of the resin film include a polyethylene terephthalate (PET) film, a polyethylene film, a polytetrafluoroethylene (PTFE) film, and a polychlorotrifluoroethylene (PCTFE) film. The illustrative examples of the non-ferromagnetic metal plate include an aluminum plate, a nonmagnetic stainless steel plate, a copper plate, and a titanium plate. Above all, from the viewpoint of handleability or a price, the use of PET film is preferable. Processing for imparting releasability may be performed on at least one face of the cover material. The thickness of the cover material is preferably 2 mm or less, particularly, from 0.5 to 0.05 mm. If the thickness of the cover material is 2 mm or less, ultrasonic vibration is sufficiently transmitted to a center portion, which is preferable.

FIG. 5 is a side view illustrating a general configuration of an apparatus used in orientation as an embodiment of the present invention. In FIG. 5, a bulk superconductor magnet is denoted by reference sign 1, and a magnetic field can be applied to a portion of the resin molded body 3. An ultrasonic vibrator is denoted by reference sign 4, and vibration can be applied to the resin molded body.

As illustrated in FIGS. 5 and 6, a magnetic field is applied to a portion of the prepared resin molded body 3 by using the bulk superconductor magnet 1. From the viewpoint of the strength of the magnetic field, it is preferable that a distance between the resin molded body 3 and the bulk superconductor magnet 1 be as short as possible. In addition, when a high thermal conductivity portion is generated inside the sheet, it is preferable that a center portion of the magnet be spaced apart from the outer peripheral edge of the sheet inside the sheet.

Next, vibration such as ultrasonic vibration is applied to a predetermined portion of the resin molded body 3 above the bulk superconductor magnet 1, by using the ultrasonic vibrator 4.

Here, vibration is used to orient the filler having magnetic anisotropy in the resin composition in a narrow region and to form a high thermal conductivity resin region 5 in which the filler has been oriented. In this case, examples of vibration include vibration generated by hitting, vibration generated by an air vibrator, ultrasonic vibration, and air vibration. The use of vibration having a frequency greater than 5,000 Hz is preferable. Of these vibrations, from the viewpoint of the easy obtainment of an apparatus or orientation in a thin-film state, the use of ultrasonic vibration having a frequency of 20 kHz or more is preferable.

The ultrasonic vibrator may apply vibration in a state where the resin molded body is heated.

A magnetic field orientation operation may be performed several times while a portion to be oriented is changed (FIG. 7).

Then, a resin sheet in which thermal conductivity is controlled can be formed by reaction-curing the oriented resin molded body or converting the oriented resin molded body into a B-stage.

In this case, as the resin composition, liquid resin composition can be used, as described above. In a case where the liquid resin composition is used, a method may be employed for forming liquid into a sheet, performing magnetic field orientation in this state or a semi-cured state, and performing curing (fully curing).

EXAMPLES

Examples and a Comparative Example are described below, and the present invention is described in detail. However, the present invention is not limited to the Examples described below.

It is noted that the viscosity of a resin composition is a measurement value at 25° measured by using a rotational viscometer described in JIS K 7117-1:1999.

A bulk superconductor magnet was prepared that has a composition of Gd—Ba—Cu—O and has a diameter of 6 cm. A bulk superconductor magnet was used that had been magnetized by using a superconducting coil magnet of 6.5 T in such a way that a center magnetic flux density is 4.5 T, a magnetic flux density at a radius of 1 cm from the center is 3 T, a magnetic flux density at a radius of 2 cm from the center is 2 T, a magnetic flux density at a radius of 2.5 cm from the center is 1 T, and a magnetic flux density at a radius of 3 cm from the center is not more than 0.1 T. As an ultrasonic vibrator used in Examples, normally a diameter of its terminal was 36 mm and its frequency was 20 kHz.

Example 1

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s; addition-curable silicone resin containing a vinyl group-containing polyorganosiloxane and a hydrosilyl group-containing polyorganosiloxane; hereinafter, similar silicone is used) is blended with 100 parts by weight of a carbon fiber (a mean length of 100 μm) that has a thermal conductivity in an axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 5 cm×5 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 2.5 cm and a width of 2.5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the results of which is illustrated in FIG. 8. The average thermal conductivity of the resin sheet was 3.7 W/mK. In this drawing, each square has a size of 1 cm×1 cm, and a numerical value in each of the squares indicates thermal conductivity (unit: W/mK) (hereinafter, the similar is applied to respective Examples and a Comparative Example).

Example 2

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 100 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 9 cm×9 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 4.5 cm and a width of 4.5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 9. The average thermal conductivity of the resin sheet was 1.8 W/mK.

Example 3

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 200 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 5 cm×5 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 2.5 cm and a width of 2.5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 10. The average thermal conductivity of the resin sheet was 6.2 W/mK.

Example 4

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 200 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 rpm within a range of 9 cm×9 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 4.5 cm and a width of 4.5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 11. The average thermal conductivity of the resin sheet was 2.6 W/mK.

Example 5

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 200 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 9 cm×9 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 2.5 cm and a width of 2.5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Next, the resin molded body was disposed in such a way that a position of a length of 6.5 cm and a width of 6.5 cm of the resin molded body is located above the center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 12. The average thermal conductivity of the resin sheet was 4.2 W/mK.

Example 6

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 400 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 9 cm×9 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 2.5 cm and a width of 2.5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Next, the resin molded body was disposed in such a way that a position of a length of 6.5 cm and a width of 6.5 cm of the resin molded body is located above the center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 13. The average thermal conductivity of the resin sheet was 4.2 W/mK.

Example 7

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 200 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 9 cm×9 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 3.5 cm and a width of 3.5 cm width of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Next, the resin molded body was disposed in such a way that a position of a length of 5.5 cm and a width of 5.5 cm of the resin molded body is located above the center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 14. The average thermal conductivity of the resin sheet was 3.7 W/mK.

Example 8

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 100 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 5 cm×5 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 5 cm and a width of 5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 15. The average thermal conductivity of the resin sheet was 2.2 W/mK.

Example 9

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 150 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 rpm within a range of 5 cm×5 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was prepared. The resin molded body was disposed in such a way that a position of a length of 2.5 cm and a width of 2.5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 16. The average thermal conductivity of the resin sheet was 6 W/mK.

Example 10

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 200 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 5 cm×5 cm at a thickness of 2 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was formed. The resin molded body was disposed in such a way that a position of a length of 2.5 cm and a width of 2.5 cm of the resin molded body is located above a center portion of the bulk superconductor magnet. Ultrasonic vibration was applied to the center portion of the magnet from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 17. The average thermal conductivity of the resin sheet was 6.3 W/mK.

Comparative Example 1

A resin composition was prepared in which 100 parts by weight of a thermosetting liquid silicone resin composition (viscosity: 0.4 Pa·s) is blended with 100 parts by weight of a carbon fiber (a mean length of 200 μm) that has a thermal conductivity in the axial direction of 900 W/mK. The resin composition was applied onto a PET film having releasability and a thickness of 100 μm within a range of 5 cm×5 cm at a thickness of 1 mm. After application, the resin composition was covered with a PET film having a thickness of 100 μm, and a periphery was blocked by a double-sided tape in order to prevent resin from leaking out, so that a resin molded body was formed. The resin molded body was disposed inside a superconducting coil magnet of 6 T having a diameter of 10 cm, and ultrasonic vibration was applied from above the film having a thickness of 100 μm. Then, the resin molded body was cured, and a resin sheet was obtained. The resin sheet was sectioned into squares of 1 cm², and thermal conductivity was measured in each of the sections, the result of which is illustrated in FIG. 18. The average thermal conductivity of the resin sheet was 12.5 W/mK.

With respect to the resin sheets obtained in the respective Examples and the Comparative Example that are described above, Table 1 described below indicates the respective items “length of carbon fiber”, “size and thickness of resin sheet”, “center position of bulk superconductor magnet in orientation”, “average thermal conductivity of curable resin sheet after magnetic field orientation”, “thermal conductivity distribution”, “ratio of area having thermal conductivity higher than average thermal conductivity of sheet by 1 W/mK or more”, “value of integer X of 5 or more by which boundary of region having thermal conductivity of X W/mK or more forms closed loop”, and “value of integer X of 5 or more by which boundary of region having thermal conductivity of X W/mK or more forms closed loop and minimum thermal conductivity inside region with closed loop as boundary is different from thermal conductivity outside region by 3 W/mK or more”.

TABLE 1 Comparative Example Example 1 2 3 4 5 6 7 8 9 10 1 Length of carbon fiber 100 100 200 200 200 400 200 100 150 200 200 (μm) Size of sheet 5 × 5 9 × 9 5 × 5 9 × 9 9 × 9 9 × 9 9 × 9 5 × 5 5 × 5 5 × 5 5 × 5 [length × width] (cm) Thickness of sheet 1 1 1 1 1 1 1 1 1 2 1 (mm) Center position of 2.5 × 4.5 × 2.5 × 4.5 × 2.5 × 2.5 2.5 × 2.5 3.5 × 3.5 5.0 × 2.5 × 2.5 × Orientation bulk superconductor 2.5 4.5 2.5 4.5 6.5 × 6.5 6.5 × 6.5 5.5 × 5.5 5.0 2.5 2.5 using super- magnet in orientation conducting [length × width] (cm) coil of 6 T Average thermal 3.7 1.8 6.2 2.6 4.2 4.2 3.7 2.2 6 6.3 12.5 conductivity of sheet (W/mK) Thermal conductivity FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. distribution of sheet 8 9 10 11 12 13 14 15 16 17 18 Ratio of area having 36 16 36 16 31 23 28 24 36 36 0 thermal conductivity higher than average thermal conductivity of sheet by 1 W/mK or more (%) Value of integer X of 5.6 5.6 6-12 5-12 6-12 6-15 5-12 None  7-10 5-12 None 5 or more by which boundary of region having thermal conductivity of X W/mK or more forms closed loop Value of integer X of None None 6-10 6-11 6-11 6-12 6-11 None 7-9 5-11 None 5 or more by which boundary of region having thermal conductivity of X W/mK or more forms closed loop and minimum thermal conductivity inside region with closed loop as boundary is different from thermal conductivity outside region by 3 W/mK or more

As described in the respective Examples above, according to the present invention, a region having a high thermal conductivity can be freely generated without joining resin by using an adhesive or the like. If a fiber length increases, as in Examples 3 and 9, thermal conductivity can significantly change by 3 W/mK or more between the inside of a region having a high thermal conductivity and the outside of the region. By performing magnetic field orientation several times, as in Examples 5 to 7, the region having a high thermal conductivity can be widened, or can be deformed. As described above, by employing the technique of the present invention, a resin molded body can be formed that has a variety of thermal conductivity distributions in a single resin molded body. In contrast, in a case where a superconducting coil magnet is used, as in Comparative Example 1, it is difficult to improve a thermal conductivity in only a portion of a sheet.

Japanese Patent Application No. 2018-188049 is incorporated herein by reference.

Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims. 

1. A resin sheet that has a single composition and that changes in thermal conductivity according to an area, wherein a region exists that has a thermal conductivity that is greater than an average value of a thermal conductivity of an entirety of the resin sheet by 1 W/mK or more.
 2. The resin sheet according to claim 1, wherein a minimum unit area of the region having the thermal conductivity that is greater than the average value of the thermal conductivity of the entirety of the resin sheet by 1 W/mK or more is 0.2 cm² or more.
 3. The resin sheet according to claim 1, wherein an area of the region having the thermal conductivity that is greater than the average value of the thermal conductivity of the entirety of the resin sheet by 1 W/mK or more is from 1 to 50% of an area of the entirety of the resin sheet.
 4. The resin sheet according to claim 1, wherein the region having the thermal conductivity that is greater than the average value of the thermal conductivity of the entirety of the resin sheet by 1 W/mK or more includes a portion having a thermal conductivity of 5 W/mK or more.
 5. The resin sheet according to claim 1, wherein a region having a thermal conductivity of 5 W/mK or more and a region having a thermal conductivity of 2 W/mK or more are included in both.
 6. The resin sheet according to claim 1, wherein one or a plurality of regions exists that is spaced apart from an outer peripheral edge of the resin sheet, is surrounded by a closed loop, and has a thermal conductivity of 5 W/mK or more.
 7. The resin sheet according to claim 6, wherein a minimum thermal conductivity of the one or the plurality of regions surrounded by the closed loop is different from a maximum thermal conductivity of a region outside the one or the plurality of regions by 3 W/mK or more.
 8. A resin sheet that is obtained by cutting off the one or the plurality of regions according to claim 6, the one or the plurality of regions having a thermal conductivity of 5 W/mK or more and being surrounded by the closed loop.
 9. The resin sheet according to any one of claim 1, wherein the resin sheet includes a cured product of a resin composition containing a filler having magnetic anisotropy.
 10. The resin sheet according to claim 9, wherein the filler having the magnetic anisotropy has been oriented in a thickness direction of the resin sheet.
 11. The resin sheet according to claim 9, wherein the filler having the magnetic anisotropy includes at least one filler selected from the group consisting of a carbon fiber, an alumina fiber, an aluminum nitride whisker, a metal nanowire, a carbon nanotube, a boron nitride nanotube, scaly boron nitride, plate-like aggregated boron nitride, scaly graphite, graphene and plate-like alumina.
 12. The resin sheet according to claim 1, wherein a resin component of the resin sheet includes silicone resin or epoxy resin.
 13. The resin sheet according to claim 1, wherein a thickness of the resin sheet is 20 mm or less.
 14. A method for manufacturing a resin sheet, the method comprising: forming a resin composition into a molded body having a sheet shape, the resin composition containing a filler having magnetic anisotropy; performing magnetic field orientation on the filler having the magnetic anisotropy by using a bulk superconductor magnet in one or a plurality of predetermined portions of the molded body; and forming a region having a thermal conductivity that is greater than an average value of a thermal conductivity of an entirety of the resin sheet by 1 W/mK or more, in the one or the plurality of predetermined portions.
 15. The method for manufacturing a resin sheet according to claim 14, wherein the resin composition includes a liquid resin composition, the liquid resin composition is applied onto a film, the magnetic field orientation is performed on one or a plurality of predetermined portions of a body coated with the liquid resin composition, and the liquid resin composition is cured. 